1. Field of the Invention
The present invention relates to a download control in a communication system, more particularly, the present invention relates to a communication system and method of controlling a process for downloading a security measure file.
2. Description of the Related Art
Upon development of network technologies in recent years, many PCs (personal computers) are connected to networks. Accordingly, damages due to computer viruses have increased, and security measures have gained importance.
As security measures for PCs, security software such as an anti-virus program is normally installed in a PC. Also, it is indispensable for security measures for PCs to apply a security patch that fixes bugs of an OS (Operating System) and applications.
Jpn. Pat. Appln. KOKAI Publication No. 2001-159975 discloses an anti-virus method that executes an anti-virus program periodically, and updates the anti-virus program itself if its version is not the latest one. Taking, as an example, one of anti-virus programs which run on PCs, a terminal updates an automatic update program to access a data file distribution server so as to get a data file of the latest version upon connection to a network.
The size of an anti-virus program and the data size of an update difference of a data file used by that program are increasingly getting bigger. When PCs are connected via a wired LAN (Local Area Network), a sufficiently broad communication band can be assured. In this case, the time required for an update process for the program and data file is short. The update process can be done without stress before the user starts a communication.
When a wireless communication is conducted using a wireless LAN, portable phone, or when a wired communication is conducted based on dial up access, a communication band broad enough for the update process cannot always be assured. Hence the update process is executed while a sufficient communication band cannot be assured. It is time-consuming, and the user gets tired of waiting for the result of the update process.
As a solution to this problem, in a security measure method proposed by Jpn. Pat. Appln. KOKAI Publication No. 2001-256045, the terminal does not take any security measures other than communications via a security server. Packets addressed to the terminal are received by the security server and analyzed to check and remove viruses. This security measure method does not require any update process on the terminal side, and does not cause any problem of the communication bandwidth.
However, since the security server bears a heavy load in this method, if the number of terminals increases, the processing performance of the security server itself cannot catch up, and the available communication bandwidth is narrowed down. Also, when the security server breaks down due to overloads imposed by, e.g., so-called DoS (Denial of Service) attacks, communications may be interrupted.
Therefore, it is desirable to take security measures not only in the security server but also in respective terminals.